Key terms and definitions for Australia's electricity markets. From dispatch intervals to carbon intensity, this reference covers the terminology used across the NEM, WEM, and energy industry.
Australian Energy Market Operator — the independent body that operates Australia’s largest gas and electricity markets and power systems. AEMO manages the NEM across five eastern states and the WEM in Western Australia, publishing dispatch data, price forecasts, and market notices.
Services that support the operation and security of the power system beyond energy supply. In the NEM, the primary ancillary service is FCAS (Frequency Control Ancillary Services), which maintains system frequency within safe operating bands.
The minimum level of electricity demand over a given period, typically met by generators that run continuously at steady output. Coal and gas-fired power stations have traditionally provided baseload generation in Australia.
Generators in the NEM submit price-quantity bids for each dispatch interval, offering to generate at up to 10 price bands. Rebidding allows generators to change the volume offered at each price band right up to the dispatch interval. Significant rebids (e.g. shifting >500 MW between bands) can indicate strategic behaviour.
The ratio of actual electricity output to maximum possible output over a period, expressed as a percentage. A wind farm with a 35% capacity factor generates 35% of what it would if running at full capacity 24/7. Typical ranges: wind 25–45%, solar 15–28%, coal 60–85%.
The amount of CO₂ emitted per unit of electricity generated, measured in tCO₂/MWh. Grid carbon intensity varies by region and time of day based on the generation mix. When renewables dominate, intensity drops; when coal or gas ramp up, it rises.
When power flows on a transmission line reach its thermal or stability limit, the line becomes congested. Congestion can cause price separation between NEM regions and force more expensive local generation to run instead of cheaper imports.
A mathematical equation in AEMO’s dispatch engine that limits power flows to keep the system within safe operating limits. Constraints can bind on transmission lines, generator groups, or system security requirements. When a constraint binds, it affects dispatch outcomes and prices.
The deliberate reduction of a generator’s output below what it could produce. Renewable generators are often curtailed when supply exceeds demand, constraints bind, or system security requires it. Curtailment represents lost revenue for wind and solar operators.
The intentional reduction or shifting of electricity consumption in response to price signals or grid conditions. In the NEM’s Wholesale Demand Response Mechanism (WDRM), loads that reduce consumption during high-price intervals (above $300/MWh) can earn wholesale market revenue.
AEMO’s central optimisation algorithm (called NEMDE) that determines generator dispatch targets and spot prices every five minutes. It minimises the cost of meeting demand while respecting network constraints and security requirements.
The five-minute period used in the NEM for pricing and generation dispatch. There are 288 dispatch intervals per day. AEMO runs the dispatch engine at the start of each interval to set prices and generator targets. The WEM uses 30-minute trading intervals instead.
Dispatchable Unit Identifier — a unique code assigned by AEMO to each generating unit or scheduled load in the NEM. Examples include BW01 (Bayswater unit 1) and ARWF1 (Ararat Wind Farm). DUIDs are used to track bids, dispatch, and generation data.
The amount of CO₂ released per unit of fuel burned to generate electricity, measured in tCO₂/MWh. Typical factors: black coal 0.88, brown coal 1.22, gas (combined cycle) 0.37, gas (open cycle) 0.70, renewables 0. Used to calculate grid carbon intensity.
Frequency Control Ancillary Services — eight market services procured by AEMO to maintain power system frequency at 50 Hz. The eight types are: Raise/Lower for each of Regulation, 6-second (Fast), 60-second (Slow), and 5-minute (Delayed). Generators, batteries, and loads can provide FCAS.
A rate paid to owners of renewable energy systems (typically rooftop solar) for electricity exported to the grid. Feed-in tariffs are set by state governments or retailers and are separate from wholesale spot prices.
The Greenhouse Gas Protocol — the international standard for measuring and reporting greenhouse gas emissions. It defines three scopes of emissions and two methods for Scope 2 reporting: location-based (using grid average factors) and market-based (using time-matched or contractual factors).
A high-voltage transmission link between NEM regions that allows electricity to flow across state borders. Major interconnectors include Basslink (VIC–TAS), Heywood (VIC–SA), QNI (QLD–NSW), and the newer VNI West (VIC–NSW). Interconnector flows are constrained by thermal and stability limits.
A device that converts direct current (DC) from solar panels or batteries to alternating current (AC) for the grid. Grid-forming inverters can also provide system strength services, which is increasingly important as synchronous generators retire.
Large-scale Generation Certificate — a tradeable certificate created when an accredited renewable power station generates one megawatt-hour of eligible renewable electricity. LGCs are a key revenue stream for large-scale wind and solar projects under the Renewable Energy Target.
Moving electricity consumption from high-price periods to low-price periods. For example, running energy-intensive equipment during overnight or midday solar windows when wholesale prices are lowest. gridIQ’s Load Shift Advisor identifies optimal windows using pre-dispatch forecast data.
A multiplier applied to a generator’s output to account for electrical losses on the transmission network between the generator and the regional reference node. An MLF of 0.95 means 5% of generated energy is lost in transmission. MLFs are published annually by AEMO and can significantly affect generator revenue.
An official notification published by AEMO to inform market participants of events, conditions, or changes. Market notices cover lack of reserve, constraint changes, planned outages, rebid explanations, and administered pricing events.
The maximum price that can be set in a NEM dispatch interval. For 2024–25, the NEM MPC is $17,500/MWh. The WEM has a separate, lower cap. The MPC exists to limit market participants’ exposure to extreme prices while still allowing scarcity signals.
The maximum rated output of a generator under standard conditions, measured in megawatts (MW). A 100 MW solar farm has a nameplate capacity of 100 MW, though its actual output varies with weather, time of day, and curtailment.
When the spot price falls below $0/MWh, meaning generators are effectively paying to stay connected to the grid. Negative prices typically occur when inflexible generators (coal, must-run contracts) cannot reduce output fast enough to match oversupply from wind and solar.
National Electricity Market — Australia’s interconnected wholesale electricity market covering Queensland (QLD1), New South Wales (NSW1), Victoria (VIC1), South Australia (SA1), and Tasmania (TAS1). The NEM operates on 5-minute dispatch intervals with prices set by a central dispatch engine.
Power stations that run primarily during periods of high demand or high prices, typically gas-fired open-cycle turbines or hydro. Peaking generators have high marginal costs but can start up quickly to capture price spikes.
Power Purchase Agreement — a long-term contract between an electricity generator and a buyer (typically a large commercial or industrial consumer) to purchase electricity at an agreed price. PPAs provide revenue certainty for renewable projects and price hedging for buyers.
AEMO’s forward-looking price and demand forecast published ahead of real-time dispatch. Pre-dispatch forecasts extend from 1 to 40 hours ahead and are updated every 30 minutes. They help market participants plan generation, load management, and trading strategies.
Renewable Energy Certificate — a generic term for tradeable certificates that represent one megawatt-hour of renewable electricity generation. In Australia, the two main types are LGCs (large-scale) and STCs (small-scale, for rooftop solar and water heaters).
The identifier used by AEMO for each pricing region. The six regions are: NSW1 (New South Wales), VIC1 (Victoria), SA1 (South Australia), QLD1 (Queensland), TAS1 (Tasmania), and WA1 (Western Australia). NEM regions use 5-minute dispatch; WA1 uses 30-minute trading intervals.
The proportion of electricity demand being met by renewable generation at a given time, expressed as a percentage. High renewable penetration reduces carbon intensity but can create operational challenges like voltage management and frequency stability.
Indirect greenhouse gas emissions from purchased electricity, as defined by the GHG Protocol. Location-based Scope 2 uses a regional annual average emission factor. Market-based Scope 2 uses time-matched emission factors reflecting the actual grid carbon intensity when electricity was consumed — rewarding organisations that shift load to low-carbon periods.
The financial process where AEMO calculates how much each market participant owes or is owed based on dispatch data, metering, and contract positions. NEM settlement moved from 30-minute to 5-minute intervals in October 2021 (known as "five-minute settlement").
The wholesale price of electricity set by AEMO’s dispatch engine for each dispatch interval. In the NEM, spot prices are set every 5 minutes per region. Spot prices can range from the market floor price (−$1,000/MWh) to the market price cap ($17,500/MWh). Most commercial electricity contracts reference or hedge against the spot price.
A measure of the power system’s ability to maintain stable voltage and withstand disturbances. Traditional synchronous generators (coal, gas, hydro) inherently provide system strength through their rotating mass. As these retire and are replaced by inverter-based renewables, system strength must be provided through other means like synchronous condensers or grid-forming inverters.
The 30-minute pricing period used in Western Australia’s WEM. There are 48 trading intervals per day. This is distinct from the NEM’s 5-minute dispatch intervals. The WEM sets energy prices, LFAS (Load Following Ancillary Services), and capacity prices separately.
The high-voltage network that carries electricity from large generators to distribution networks. In Australia, transmission is managed by Transmission Network Service Providers (TNSPs) in each state. Transmission constraints and losses directly affect wholesale prices.
Transmission Use of System charges — fees paid by electricity users and generators for using the high-voltage transmission network. TUOS charges are a significant component of commercial electricity bills and vary by location and connection type.
Volume-Weighted Average Price — the average spot price over a period, weighted by the volume of electricity traded in each interval. VWAP provides a more meaningful average than a simple arithmetic mean because it accounts for demand patterns. Time-of-use VWAP (peak, off-peak, shoulder) is commonly used in contract pricing.
Wholesale Electricity Market — Western Australia’s standalone electricity market, operated by AEMO but separate from the NEM. The WEM uses 30-minute trading intervals, has a separate capacity market, and covers the South West Interconnected System (SWIS) around Perth.
Understanding the terminology is the first step. gridIQ turns these concepts into live, actionable intelligence — real-time prices, carbon intensity, generation mix, and AI-powered analysis across all six Australian energy regions.
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